Enamino Ketones Research Articles

An Efficient Propylphosphonic Anhydride (T3P®)-Mediated MW-induced Solvent-free Rapid Synthesis of Enamino Esters and Ketones including 5, 5-Dimethyl-3-aminocyclohex-2-enones

Abstract: This work presents a clean and convenient synthesis of various β-enaminones including 5,5- dimethyl-3-aminocyclohex-2-enones, in satisfactory to excellent yields from the condensation reaction of primary amines with β -dicarbonyls by employing T3P® as a catalyst and performing the reaction under microwave irradiation and solvent-free conditions. These rapid reactions launched readily and stood a diversity of organic functional groups. A mixture of 1,3-dicarbonyl compound, primary amine and T3P® (50% in AcOEt) was irradiated for an appropriate time under microwave at 80°C. After completing the reaction (TLC) and cooling to r.t., ethyl acetate and saturated aqueous NaHCO3 solution were added. The aqueous phase was extracted ethyl acetate. The combined organic layer was washed with brine, dried over Na2SO4, and filtered, and the solvent was removed under reduced pressure to afford the product, which was recrystallized from diisopropyl ether. The presented results exhibit a better catalytic activity of T3P in the synthesis of enaminones. It could be concluded that T3P is the best catalyst as it took only a few minutes for the completion of the reaction with an excellent yield of product, which indicates T3P is more efficient, compared to other catalysts. A comparison of the efficiency of the present procedure with some heterogeneous solid catalysts was evaluated as well. Clearly, a higher yield was established in this procedure compared to other catalysts. Furthermore, the reaction of amines with dimedone was investigated as well, delivering excellent yields. The reaction catalyzed by T3P under microwave irradiation supplies a comprehensive method for the synthesis of enaminones. In this work, T3P is an effective, efficient and green catalyst, which forms the procedure economic, suitable, and safe with widespread application in the synthesis of enaminones. background: This work presents a clean and convenient synthesis of various β-enaminones incuding 5,5-dimethyl-3-aminocyclohex-2-enones in good to excellent yields from the reaction of different primary amines with 1,3-dicarbonyl compounds by employing T3P® as a catalyst and performing the reaction under microwave irradiation and solvent-free conditions. This one-pot rapid reaction proceeded readily and tolerated a variety of functional groups.

An efficient synthesis of 3-fluoro chromones from the tandem cyclization of enaminones by using N-Fluoro benzenesulfonimide

An efficient method of synthesizing the various 3-Fluorochromones from enamino ketones by using N-Fluoro benzenesulfonimide (NFSI) is described. The key step in the synthesis involves tandem cyclization and fluorination to form 3-fluorochromones in good yields. The significant features of this method include simple operational procedures, high purity of the product and cost reducing. This reaction achieved good to excellent yields (51–92%) under ambient conditions with significantly faster rate. The products obtained were confirmed by 1H, 13C NMR and mass spectroscopy techniques.

Langlois Reagent Mediated Tandem Cyclization of o-Hydroxyaryl Enaminones for the Synthesis of 3-(Trifluoromethyl)chromones

AbstractAn efficient and simple synthesis of various 3-(trifluoromethyl)chromones from enamino ketones is described. The key step in the synthesis involves the introduction of a trifluoromethyl (CF3) moiety onto a chromone structure. The significant features of this method include simple operational procedures, the high purity and yield of the product, and excellent regioselectivity.

Bioinspired AgNPs: Effective and Recyclable Catalysts towards the One‐Pot Synthesis of Hexahydroquinoline Derivatives via Three‐Component Coupling Reaction

AbstractGreen synthesis of silver nanoparticles (AgNPs) was carried out using aqueous bark extract of Shorea robusta(Sal tree) as the reducing and capping agent. AgNPs were characterized using modern characterization tools like UV‐Vis, PXRD, FT‐IR, SEM, and HR‐TEM. The catalytic application of the prepared AgNPs in three‐component coupling reaction of aldehyde, malononitrile, and cyclic enamino ketone resulted in good to excellent yields of hexahydroquinoline derivatives. Moreover, the catalyst can be recycled up to 5 times without compromising too much yield. The mechanistic pathway was investigated employing GC‐Mass spectroscopy and supported through the Density Functional Theory (DFT) calculations. A two‐step mechanism has been proposed for the coupling reaction, and the presence of electron‐withdrawing group in the aldehyde component is found to be more favorable than electron‐releasing one in terms of yield with lesser time.

A three-component condensation of cyclic enamino ketones, phenylglyoxal hydrate, and ethyl cyanoacetate

A three-component condensation of cyclic enaminones, phenylglyoxal hydrate, and ethyl cyanoacetate in EtOH gave a number of 4,5,6,7-tetrahydroindole functional derivatives. The corresponding intermediates, 2,3,4,5,6,7-hexahydroindoles, are formed under mild conditions. Under more severe conditions (heating under reflux in DMF), cleavage of the ethoxycarbonyl group takes place.

Synthesis of N-Alkyl Enamino Ketones Based on 3-Acyl-4H-polyfluorochromen-4-ones and Their Antimicrobial Activity

New N-substituted enamino ketones were synthesized by directed transformation of 3-acetyl- and 3-benzoyl-5,6,7,8-tetrafluoro-4H-chromen-4-ones by the action of highly basic primary amines as a result of opening of the pyranone ring and deacylation. The synthesizedN-hexyl and N-octyl derivatives were evaluated for fungistatic and bacteriostatic activities.

Reactions of perfluoroacylchromenes with aromatic amines: synthesis of perfluoroalkylchromene carbaldehydes

The reactions of 3-perfluoroacyl-4Н-chromenes and 2-perfluoroacyl-1Н-benzo[f]chromenes with primary aromatic amines resulted in pyran ring cleavage, which was initiated by an aza-Michael reaction. The obtained enamino ketones underwent rearrangements in the presence of superacids, giving 2-perfluoroalkyl-4Н-chromene-3-carbaldehydes and 3-perfluoroalkyl-1Н-benzo[f]chromene-2-carbaldehydes, respectively.

Peroxy‐Benzoic Acid Mediated Domino C[sp2] Hydroxylation /Annulation of Enaminones for the Synthesis of 3‐Hydroxy Chromones

AbstractAn efficient, facile, and clean synthesis of various 3‐hydroxy‐chromones (3‐hydroxy‐4H‐chromene‐4‐ones) via enamino ketone followed by cyclization using m‐chloroperbenzoic acid (MCPBA) has been described. The significant features of this method include simple method, high purity and excellent regio‐selectivity of the products. This is the first report for the two step one pot synthesis of 3‐hydroxyl chromone using MCPBA.

Synthetic Approach to Fused Azasultams with 1,2,4-Thiadiazepine Framework

Synthetic approach to fused azasultams with 1,2,4-thiadi­azepine framework via base promoted protocols has been developed. 1H-Azole-2-carboxylates and N-(chloromethyl)-N-methylmethanesulfonamide were used as ambiphilic building blocks in the one-pot and two-step reaction sequences. Chemical behavior of the obtained azasultams in reactions with amines, hydrazine, DMFDMA, and NaBH4 was investigated. An enamino ketone derived from an azasultam was exploited in the synthesis of new pyrazole and pyrimidine heterocycles.

Selective synthesis of 2‐(5‐oxo‐1‐arylhex‐1‐yn‐3‐yl)phenyl benzoates via FeCl3‐mediated cascade reactions of propargylamines with β‐enamino ketones

A mild and efficient FeCl3‐mediated cascade reaction of ortho‐hydroxyl propargylamines with β‐enamino ketones has been developed. This protocol provided a practical and selective method to synthesize 2‐(5‐oxo‐1‐arylhex‐1‐yn‐3‐yl)phenyl benzoates via in situ generated alkynyl o‐quinone methides following a cascade intermolecular 1,4‐conjugate addition/intramolecular nucleophilic addition/reverse Claisen condensation/hydrolysis pathway. Furthermore, a series of 2‐(3‐oxo‐1‐arylbutyl)phenyl benzoates with good functional group tolerance were prepared in good to high yields under these reaction conditions.

Selectfluor-Mediated Tandem Cyclization of Enaminones for the Synthesis of 3-Fluorochromones

An efficient synthesis of various 3-fluorochromones (3-fluoro-4H-chromene-4-ones) from enamino ketones by using Selectfluor is described. The key step in the synthesis involves tandem fluorination and cyclization to form 3-fluorochromones in good yields. The significant features of this method include simple operational procedures, a high purity of the product, and excellent regioselectivity.

Three-Component Condensation of Cyclic Enamino Ketones with Phenylglyoxal Hydrate and Ethyl Acetoacetate

Three-component condensation of cyclic enamino ketones with phenylglyoxal hydrate and ethyl acetoacetate in aqueous ethanol afforded a series of polyfunctionalized 3,3a,4,5,6,7,8,8a-octahydro-2H-furo-[2,3-b]indole derivatives.

Fluorescent Probes from Aromatic Polycyclic Nitrile Oxides: Isoxazoles versus Dihydro-1λ3,3,2λ4-Oxazaborinines.

Anthracenenitrile oxide undergoes 1,3‐dipolar cycloaddition reaction with propargyl bromide affording the expected isoxazole as single regioisomer, suitably synthetically elaborated and functionalized with a protected triple bond. The introduction of a bromine atom at the position C10 of the anthracene moiety allows for inserting a variety of aromatic and heterocyclic substituents through Suzuki coupling. A two‐way synthetic route can lead to simple isoxazole derivatives or, after N−O bond reductive cleavage and BF3 complexation, enamino ketone boron complexes. The photophysical properties of both the substituted isoxazoles and the corresponding boron complexes were investigated to show the potentialities for the employment as fluorescent tags in imaging techniques. The quite good quantum yield values confirm the suitability of these compounds in the cellular environment. Scope and limitations of the methodology are discussed.

Thiocyanation of Enamines of the 3,3-Dialkyl-1,2,3,4-tetrahydroisoquinoline Series

Thiocyanation of secondary enamines of the 3,3-dialkyl-1,2,3,4-tetrahydroisoquinoline series and their benzo[f]-fused analogs (esters, amides, ketones, and nitriles) with thiocyanogen generated in situ afforded thiazolo[4,3-a]isoquinoline derivatives. Analogous reaction with a tertiary enamino ketone gave product of hydrogen substitution at the β-carbon atom of the enamine fragment.

Reaction of cross-conjugated push-pull enamino ketones with 1,2-naphthoquinone 1-methides: synthesis of 3-aryl-1-(1H-benzo[f]chromen-2-yl)prop-2-en-1-ones

A series of 3-aryl-1-(1H-benzo[f]chromen-2-yl)prop-2-en-1-ones, both unsubstituted and containing an aryl substituent at the C-1 position was obtained via the reaction of cross-conjugated push-push enamino ketones with 2-naphthol-derived Mannich bases. The cascade process involves the hetero-Diels–Alder reaction between 1,2-naphthoquinone 1-methide formed in situ and an enaminone, followed by the elimination of a dimethylamine molecule.

New Conjugates of Di- and Trichlorocyclopentenones with Amino Derivatives of Adamantane and Amino Acids

Reactions of di- and trichlorocyclopentenones with adamantan-1-amine, 1-(adamantan-1-yl)ethanamine, and amino acids (histidine, L-proline, L-methionine methyl ester hydrochloride) afforded the corresponding enamino ketones.

An Efficient Microwave-Assisted Propylphosphonic Anhydride (T3P®)-Mediated One-Pot Chromone Synthesis via Enaminones

An efficient synthesis of 4H-chromene-4-ones via enamino ketones, with cyclization by using T3P® under microwave heating is described. This is the first report for the synthesis of chromones by using T3P®. Significant features of this method include short reaction times and high-purity products.

Reaction of 2-chloromethylphenols with enaminones

The reaction of o-(chloromethyl)phenols with enamino ketones afforded a series of 3-acyl- and 3-formyl-4H-chromenes as a result of cascade transformation including [4 + 2]-cycloaddition of enamino ketone to o-quinone methide generated in situ and subsequent elimination of secondary amine.

Three-component synthesis of 5-aryl-1,8-naphthyridine-3-carbonitriles

A procedure has been developed for the synthesis of highly functionalized 1,8-naphthyridines by three-component condensation of aromatic aldehydes with malononitrile dimer and enamino ketones.

ChemInform Abstract: Regioselective Construction of Diverse and Multifunctionalized 2‐Hydroxybenzophenones for Sun Protection by Indium(III)‐Catalyzed Benzannulation.

AbstractThe title compounds are prepared by the highly regioselective indium(III)‐catalyzed benzannulation reaction between benzopyran derivatives and β‐enaminoesters or ‐enamino ketones.